12 May

William Harvey (1578–1657) was the eldest of seven sons born to Thomas Harvey, and the only member of this family of merchants and landowners to become a physician. After earning the Bachelor of Arts degree from Caius College, Cambridge, in 1597, Harvey followed the footsteps of the great English humanist-scholars to Padua. In 1602, Harvey returned to England and established a successful medical practice. His marriage to Elizabeth Browne, the daughter of Lancelot Browne, physician to Queen Elizabeth I and James I, gave him access to the highest court and professional circles. In rapid succession, Harvey was elected Fellow of the College of Physicians, appointed physician to St. Bartholomew’s Hospital, Lumleian Lecturer for the College of Physicians, and physician extraordinary to James I. Harvey retained the latter position when Charles I became king in 1625 and was pro- moted to physician in ordinary in 1631 and senior physician in ordinary in 1639. (As strange as it may seem, ordinary in the court medical hier- archy was more prestigious than extraordinary.) As one of the king’s physicians, Harvey was charged with some peculiar assignments, such as the diagnosis of witchcraft, an area of considerable interest to James I. Harvey’s duties also entailed extensive travels with King Charles I and service during the Civil War. It was at the request of the king that Harvey performed one of his most unusual

William Harvey

William Harvey.

autopsies, the postmortem of Thomas Parr, who had claimed to be the oldest man in England. Brought to London in 1635, Old Parr was presented to Charles I, and exhibited at the Queen’s Head Tavern. Life in London undermined Parr’s good health and he soon died, supposedly 152 years old. From the autopsy results, Harvey concluded that pleuropneumonia was the cause of death, but others thought it might have been old age. Harvey may have inspired a revolutionary approach to experi- mental biology and human physiology, but professionally and socially he was a man whose conservative demeanor and outward conformity generally protected him from political intrigues and professional rival- ries. Throughout the battles between the followers of King Charles I and the parliamentary forces under Oliver Cromwell (1599–1658), Harvey remained loyal to his king. After the Royalists were defeated and King Charles was publicly beheaded in 1649, Harvey retired to live with his brothers in the countryside near London. Tormented by gout and deteriorating health, he apparently became addicted to opium and may have attempted suicide more than once. Notes for his Lumleian Lectures suggest that Harvey arrived at an understanding of the motion of the heart and blood well before 1628, when An Anatomical Treatise on the Motion of the Heart and Blood in Animals (usually referred to as De motu cordis) was published.

Perhaps Harvey delayed publication because, as he confessed in his book, his views on the motions of the blood were so novel and unprec- edented that he was afraid he would ‘‘have mankind at large for my enemies.’’ Considering that Harvey, like all medical students for hundreds of years, had been force-fed a steady diet of Galenism, and that conformity was generally the ticket to success and advancement within an extremely conservative profession, how was it possible for Harvey to free himself from the past? Rather than finding it remarkable that generations of physicians had meekly accepted Galenism, we should be moved to won- der how Harvey was able to realize that the grand and elegant doctrines about the motions and functions of the heart and blood that were universally accepted by his teachers and fellow students were wrong. When reading De motu cordis, one is struck most by the thought that in principle, Harvey’s experiments and observations could have been performed hundreds of years before. During the seventeenth century, new instruments, such as the telescope and microscope, literally opened up new worlds to science and imagination, but Harvey’s work was performed without the aid of the microscope.

Like Aristotle, whom he greatly admired, Harvey asked seemingly simple but truly profound questions in the search for final causes. In think- ing about the function of the heart and the blood vessels, he moved closer to Aristotle’s idea that the heart is the most important organ in the body while he revealed the errors in Galen’s scheme. Harvey wanted to know why the two structurally similar ventricles of the right and left heart should have such different functions as the control of the flow of blood and of the vital spirits. Why should the artery-like vein nourish only the lungs, while the vein-like artery had to nourish the whole body? Why should the lungs appear to need so much nourishment for themselves? Why did the right ventricle have to move in addition to the movement

William  Harvey’s De motu cordis

William  Harvey’s   De  motu  cordis  (courtesy   of  the  National   Library   of Medicine).

of the lungs? If there were two distinct kinds of blood—nutritive blood from the liver distributed by the veins and blood from the heart for the distribution of vital spirits by the arteries—why were the two kinds of blood so similar? Such questions were not unlike those that Harvey’s contemporaries were prepared to ask and debate. Using arguments based on dissection, vivisection, and the works of Aristotle and Galen, Harvey proved that in the adult, all the blood must go through the lungs to get from the right side to the left side of the heart. He proved that the heart is muscular and that its most important movement is contraction, rather than dilation. But his most radical idea was that it was the beat of the heart that produced a continuous circular motion of the blood. In warm-blooded animals, the systole (contraction) and diastole (expansion) of the heart are so rapid and complex that Harvey at first feared that only God could understand the motion of the heart. He solved this problem by using animals with simpler cardiovascular systems and a slower heartbeat, such as snakes, snails, frogs, and fish. With cold-blooded animals, or dogs bled almost to death, Harvey was able to create model systems that essentially performed in slow motion.

When observations and experiments were properly analyzed, it was apparent that the motion of the heart was like that of a piece of machin- ery in which all the parts seemed to move simultaneously, until one understood the motions of the individual parts. Harvey also posed a question of child-like simplicity that modern readers find most compelling, because the answer seems to be totally incompatible with Galenic theories. Yet, if this aspect of his work is overemphasized, it tends to remove Harvey from his seventeenth- century context and makes him appear more modern in outlook and approach than is really appropriate. Harvey asked himself: How much blood is sent into the body with each beat of the heart? Even the most cursory calculation proves that the amount of blood pumped out by the human heart per hour exceeds the weight of the entire individual. If the heart pumps out 2 ounces of blood with each beat and beats 72 times per minute, 8640 ounces (2 72 60), or 540 pounds, of blood is expelled per hour.

Whether calculated for humans, sheep, dogs, or cat- tle, the amount of blood pumped out of the heart in an hour always exceeds the quantity of blood in the whole animal, as demonstrated by exsanguination. Skeptical readers could go to a butcher shop and watch an experienced butcher exsanguinate an ox. By opening an artery in a live animal, the butcher can rapidly remove all the blood. It is all too easy to assume that these arguments should have provided an immediate deathblow to the Galenic system. However, the kind of evidence that appears most compelling today did not necessarily appeal to Harvey’s contemporaries. Arguing from experimental and quantitative data in biology was remarkable in an era when even phys- icists were more likely to speculate than to weigh and measure. More- over, opponents of Harvey’s work presented what seemed to be quite logical alternatives, at least in light of accepted Galenic theory. For example, some critics argued that the heart attracted only a small amount of blood from the liver, where sanguification (the formation of blood) occurred.

This blood foamed and expanded to such a great extent under the influence of the heat of the heart that the heart and arteries appeared to be full. Furthermore, multiplying the putative volume of blood discharged by the heart by the number of beats per minute was meaningless, because it was not necessary to assume that blood was driven from the heart through the arteries with each heartbeat. Having solved the mechanical problem of the motion of the heart and blood, and demonstrated the true function of the venous valves, Harvey generally avoided arguments about the generation and distri- bution of the various kinds of spirits. Harvey had demonstrated the errors in Galen’s system and had discovered essentially all that could be known about the structure and function of the cardiovascular system without the use of the microscope. Thus, one of the major gaps in Harvey’s work was his inability to identify the structures joining the arterial and the venous system. He was forced to close this gap with hypothetical anastomoses or pores in the flesh.

As scientists like Marcello Malpighi (1628–1694) extended the limits of anatomical study with the microscope, the capillary network completed the cardiovas- cular system. Also unfinished at the time of Harvey’s death was a book he planned to publish about his ideas on disease. The manuscript for this book may have been among those destroyed during the Civil War. Because of this loss, Harvey’s concept of how knowledge of the cir- culation might solve questions about disease and medical practice must be constructed by piecing together comments made in his surviving works. De motu cordis promised that the new understanding of the circulation would solve many mysteries in medicine, pathology, and

William Harvey’s demonstration

William Harvey’s demonstration of the role of the venous valves in the circulation of the blood.

therapeutics. In  later  works,  Harvey  alluded  to  his ‘‘Medical  Obser- vations,’’ but no such book  was ever published.

Replacing  the  Galenic  system  that  had  so  thoroughly, if incor-rectly, explained  the purpose of the heart,  lungs,  liver, veins, arteries, and  spirits  was completely  beyond  Harvey’s  technical  and  theoretical methods and goals. For seventeenth-century physicians, the new theory of the circulation  raised more questions than it answered. If Harvey was correct, how could all the vital phenomena that Galenism had dealt with so long and  so well be explained? For  example, if the tissues did not consume the blood, how did they secure their nourishment? If the blood was not continuously formed from food by the liver, how was it synthesized? If the  blood  moved  in a closed,  continuous circle, what was the purpose  of the arterial  and  venous  systems and  how did  the body  accomplish  the  generation   and  distribution  of  the  vital  spirit and the innate heat? If the venous blood  did not originate  in the liver, which  had  such  a  central  role  in  the  Galenic  system,  what  was  the function of this organ? If vital spirit was not produced  by the mixture of air and blood in the lungs or in the left ventricle of the heart, what was the function  of respiration? What  was the difference between  arterial and  venous  blood  if all of the  blood  was constantly  recirculated? If Galen were incorrect  about  the anatomy  and physiology of the human body, what principles would guide medical practice?

Like almost all fundamental discoveries, Harvey’s work provoked an avalanche of new questions and a storm of controversy.  Many critics were unable  or  unwilling  to  understand the  implications  of Harvey’s work. Others found it impossible to give up the old Galenic system that had provided  all-encompassing  rationalizations for health  and disease, diagnosis,  and  therapeutics. How  could  medicine  be  saved  if Galen was sacrificed for the sake of Harvey’s  radical  theory? The theory  of continuous  circulation   raised  many  disturbing   questions   for  which Harvey   provided   no  answers.   Such  questions   stimulated   Harvey’s admirers to embark on new experimental  ventures, while critics denoun- ced his theory  as useless, false, impossible,  absurd,  paradoxical, and harmful.

Well  aware  of  the  revolutionary  nature   of  his  work,   Harvey predicted  that  no one under  40 would understand it. His work consti- tuted a revolution  in science worthy of comparison  to that  launched  by Sir Isaac Newton. Although  illness, age, and the loss of precious materi- als and manuscripts  during the Civil War prevented Harvey from accomplishing  all his goals, he did live to see his followers establish  a new experimental  physiology  inspired  by his ideas and  methods.  The questions raised by Harvey’s work provided the Oxford physiolo- gists—men such as Robert  Boyle, Robert  Hooke,  Richard  Lower, John Mayow,  and  Christopher  Wren—with  a  new  research  program   for attaining  a better  understanding of the workings of the human  body.

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